Polymer particles, such as polyethylene particles, have been used in various industrial fields such as a material for separators in a lithium-ion battery. Although the polymer particles can be synthesized by various methods, high manufacturing expenses and environmental pollution have remained as important problems in manufacturing the polymer particles. Therefore, there has been a demand for the polymer particle manufacturing process process that is more energy- and cost-efficient, and environmentally friendly. Also, for the process to be widely applicable in various industrial fields, there has been a demand for the process capable of accurately controlling the average diameter of the polymer particles.
Conventional polymer particle manufacturing processes are carried out with the need to heat the mixture solution of a good solvent in which a polymer is dissolved and a non-solvent in an excessive amount, to or above the melting point of the polymer. That is, in the conventional manufacturing processes, not only the good solvent but also the non-solvent is heated to or above the melting point of the polymer, leading to an increase in the operating and fixed costs of the process, and a difficulty in achieving standardization of a manufacturing process and mass-production.
FIG. 1 and FIG. 2 are the diagrams illustrating examples of conventional polyethylene manufacturing processes.
In the manufacturing process shown in FIG. 1, for example, both a good solvent in which low-density polyethylene is dissolved, such as dodecanol in which low-density polyethylene is dissolved, and a non-solvent are heated to or above the melting point of the polyethylene and subsequently cooled, and during the cooling, a dense emulsion is produced through inducing phase separation between the good solvent and the non-solvent, and polyethylene is produced through inducing crystallization within the emulsion. In this process, in order to induce the temperature-dependent emulsification, it is required that the good solvent and non-solvent are not miscible at low temperatures but miscible at higher temperatures, and examples of such a non-solvent may include ethylene glycol, diethylene glycol, and triethylene glycol. Also, polyethylene particles can be obtained by filtering the crystal solution resulted from the crystallization using a filteration device, after which the residual solvent and non-solvent in the polyethylene are completely removed using a washing solvent such as hexane, acetone and ethanol. However, as previously discussed, manufacturing processes like the one illustrated in FIG. 1 is likely to have the disadvantage of a high operating cost, because the process requires heating of both the good solvent and non-solvent to or above the melting point of polyethylene.
Also, the manufacturing process illustrated in FIG. 2 is similar to the emulsion crystallization process of the manufacturing process illustrated in FIG. 1, except that the emulsion crystallization is carried out using a continuous reactor, more particularly, a microreactor. However, both processes have the disadvantages in that they require costly manufacturing facilities and are difficult to adapt to mass-production, and further, the concentration of polymer in solvents needs to be maintained relatively low, because the narrow channels of a micromixer are prone to clogging due to rapid crystallization of a polymer inside the channels of a microreactor.